1. Field of the Invention
The present invention relates in general to electroconductive adhesive tapes used for fixing an explosion protective band to a Braun tube and, more particularly, to a structural improvement in such tapes for not only improving the adhesive strength between the base of an electroconductive adhesive tape and a thermoplastic resin layer such as a polyethylene layer, but also preventing the static electricity from accumulating in the Braun tube.
2. Description of the Prior Art
Since a Braun tube is conventionally made of glass and in a vacuum condition in its interior, the Braun tube may be easily damaged by an outside impact. In order to prevent the outside impact from being directly applied to the Braun tube itself, the Braun tube is not directly fixed to a housing (or a casing) of a television set but indirectly fixed to the housing by means of an explosion protective band. This explosion protective band is made of a metal and attached to the outer edge of the Braun tube. The explosion protective band absorbs the outside impact and thereby prevents the Braun tube from being suddenly damaged by the impact. As the explosion protective band is attached to the edge of the Braun tube, the fragments of the Braun tube may be merely scattered for a short distance when the Braun tube suddenly explodes by a very powerful outside impact. The explosion protective band also effectively discharges the static electricity of the Braun tube to the outside and thereby prevents the static electricity from accumulating in the Braun tube.
When the explosion protective band is mounted to the outer edge of the Braun tube, an adhesive tape is used.
The Braun tube of an image receiving apparatus such as a television set or a video display terminal is applied with a high voltage in its interior when an image is produced on the screen of the Braun tube. Due to the above high voltage, static electricity is generated on the outer surface of the Braun tube. The static electricity must be removed from the Braun tube; otherwise the static electricity will accumulate on the outer surface of the Braun tube and cause several problems as follows.
Since the Braun tubes have various uses, a user has many opportunities to touch with the Braun tube by the hand or body. The static electricity accumulating in the Braun tube exerts a bad effect on the user's body as well as on the operational performance of the Braun tube. For example, when a user is brought into contact with the Braun tube charged with the static electricity, the user may be susceptible to disease and also may feel discomfort. In addition, the static electricity may disturb the electric circuit of the apparatus. The static electricity may also shake the image produced on the screen of the Braun tube.
Recently, many attempts have been made to prevent the static electricity from accumulating in the Braun tube. For example, an electroconductive adhesive tape, which was prepared by coating an electroconductive material, such as graphite, on an aluminum or copper foil, is cut into several pieces having a predetermined length. The tape pieces in turn are attached to the outer edge of Braun tube at regular intervals. Thereafter, an explosion protective band is attached to the adhesive tape pieces such that band and tape pieces are electrically connected to each other. With the electroconductive adhesive tape and the explosion protective band attached to the Braun tube, the static electricity generated from the Braun tube can be discharged to the outside through the tape and band and in turn through a grounding circuit provided in the housing.
A high precision image receiving apparatus, such as a computer monitor, a large-sized color television set or a high definition television set, uses a color display tube (CDT). In order to remove the static electricity and to block electromagnetic waves emitted from the screen of the CDT, such a CDT may be coated with electroconductive ceramics.
However, the conventional electroconductive adhesive tape used for fixing the explosion protective band to the Braun tube has a problem as follows. That is, the base of the conventional adhesive tape is formed of woven fabrics with a network structure into which glass fibers are woven. The above woven fabrics with network structure used as the conventional tape's base are noted to have a high tensile strength. However, since one side of the above woven fabrics of the tape's base has no adhesive strength with a thermoplastic synthetic resin layer such as a polyethylene layer, the above tape's base must be additionally treated to improve its adhesive strength when the tape is used for fixing the explosion protective band to the Braun tube.